Methods for the covert transmission of data for identification

ABSTRACT

A method for determining an identifier of a conditional access card used in a conditional access system, in which the conditional access card autonomously modulates the timing of data packets sent by the conditional access card, according to a sequence that depends on the identifier of the card. The sequence is generated by a predefined non-linear function stored on the conditional access card, and the predefined non-linear function depends on both the identifier of the conditional access card and a non-linear random sequence that is known to the conditional access card and a monitoring station that receives transmissions from the conditional access card.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of co-pending U.S. patent applicationSer. No. 13/512,083, entitled, “Card Sharing Countermeasures,” filedOct. 18, 2012, which is a National Stage of International ApplicationNo. PCT/IB2009/007825 filed Nov. 25, 2009, the contents of which areincorporated herein by reference in their entirety.

FIELD OF THE INVENTION

The present invention relates generally to the Pay-TV piracy field andmore particularly to card sharing attack.

BACKGROUND OF THE INVENTION

Thanks to the notable improvement in digital broadcasting platformswhich contribute towards a broader reception of digital contents, Pay-TVis ever evolving and gaining more and more audiences. However, thisevolvement has to be escorted by security measures as hackers areunceasingly looking for new issues and vulnerabilities so as to acquirean unauthorized reception on their satellite or cable TV system.

Hence, in order to protect their investments and safeguard their revenuestreams, Pay-TV providers have to rely on a strict Conditional AccessSystem (CAS). CAS is responsible for ensuring that broadcasted contentsare accessible only to those customers who have satisfied clearlyspecified conditions, mainly payment related.

To that end, the CAS involves two main components: a source-sidecomponent, and a reception-side component.

At the source-side, the digital content to be broadcasted (includingvideo, audio and data) and which the provider wishes to restrict access,is encrypted (by using common DVB scrambling algorithms) with acryptographic key, called a Control Word (CW). The CW is generated by apseudo-random binary sequence generator (CW Generator). More generally,the CW is changed every few seconds (mostly, with a periodicity between2 and 10 s).

Since there is no return channel or any other means to negotiate withlegitimate Satellite or Terrestrial receivers, the CW, in turn, needs tobe protected then carried by the broadcasted content itself. The CW is,thus, encrypted with a function specific to each CAS manufacturer, andis then packaged into so-called Entitlement Control Message (ECM).

Further, the Viewing rights of the individual subscriber is managed bythe so called Subscriber Management System (SMS) and updates or changesin rights are packaged with entitlement data into so-called EntitlementManagement Message (EMM).

Therefore, the resulting scrambled content, ECM, and EMM are broadcastedtogether in the same channel in only one scrambled stream.

At the reception-side, the CAS, mainly, includes an IntegratedReceiver/Decoder (IRD), Television and a smart card, which are generallyboth comprised within a Set-top box (STB).

The IRD receives the scrambled streams which comprises the encryptedcontent, the ECM and the EMM. The IRD filters from the received streamthe ECM and the EMM according to the parameters provided by the card andthen forwards these messages to the card.

If the card belongs to the right broadcaster and is not revoked, thenthe card decrypts the ECM into a plain CW and transfers it back to theIRD so that IRD will be able to descramble the scrambled content (VideoImage).

The descrambled content is then forwarded to a terminal user able todisplay such stream as a television or a computer.

The CW is very vulnerable to the link between the card and the IRD. Infact, by eavesdropping the communication of the card, an attacker mayeasily redirect the decrypted CW to others IRD to descramble theencrypted content. In other words, an attacker can effortlessly obtainthe CW in the plaintext form while its transmission from the card to theIRD. Therefore, the attacker can distribute the obtained CW throughInternet or radio means to unauthorized users so that they freely enjoythe protected content, without any subscription.

Such attack is known as “control word redistribution”, “CW sharing”, or“card sharing”, by which one legitimate user colludes to an unrestrictednumber of illegitimate users to provide unauthorized access to aprotected content. In particular, by acting as a card server in a pushsystem or a pull system way, only one legitimate card can providenumerous illegitimate receivers with free-access to an encryptedcontent, resulting in a serious threat to the security of the CAS.

In a push system, the card sharing pirate runs one or more IRD's,intercepts the CWs and sends all of them to clients. A client softwareapplication selects the needed CW for the watched channel out of thewhole packet and loads it into its IRD's.

In a pull system one or more card, connected to a card server running ona PC are shared among Clients. As soon as an ECM is received by a clientIRD, it is forwarded to the card server in order to be processed. Thecard server subsequently carries out the message decryption and forwardsback to each client the decrypted CW. As a forward channel is needed toprovide the ECM, such implementation can be deployed only on two-wayconnections, namely on Internet network.

Even if Pay-TV providers resort to—frequently changing the CW, cardsharing remain possible as the crypto period (generally around 7seconds) is relatively greater than the required time to provide, inreal-time, the CW to almost any person on the planet.

Accordingly, card sharing is more and more popular among networkcommunities as it is powerful and easily deployable (no exhaustive smartcard compromising or IRD manipulating) which makes of card sharingattack a significant security threat to be overcome.

It is in one object of the present invention to counteract card sharingattack.

Another object of the present invention is to remotely identify a sharedcard.

Another object of the present invention is to provide a method for cardsharing prevention with the least modification on the underlying CAShardware.

Another object of the present invention is to remotely identify a sharedcard, whatever deployed in a push system or a pull system manner.

Another object of the present invention is to be able to remotelyidentify a plurality of cards which are jointly shared via a cardserver.

Another object of the present invention is to provide a lowcomputational complexity method for remotely identifying a shared card.

Another object of the present invention is to provide a method forretrieving the identifier of a shared card without any functionaldisturbance of the IRD.

Another object of the present invention is to pinpoint the identifier ofa shared card in an invisible way for card sharers.

Another object of the present invention is to provide CAS managers witha plurality of decisions against shared card owners.

Another object of the present invention is to permit a remoteidentification of a shared card from almost any access point to thepirate network.

Another object of the present invention is to provide an outgoingcommunication method for the card.

Another object of the present invention is to cleverly dissimulate theidentifier of the card in its outgoing communication.

BRIEF DESCRIPTION OF THE DRAWINGS

The objects, advantages and other features of the present invention willbecome more apparent from the following disclosure and claims. Thefollowing non-restrictive description of preferred embodiments is givenfor the purpose of exemplification only with reference to theaccompanying drawings in which:

FIG. 1 is a block diagram showing a monitoring station connected to thepirate network in order to remotely recover the identifier of a sharedcard;

FIG. 2 is a block diagram illustrating one embodiment of outgoingcommunication of a card, upon the reception of a CW request, whateverfrom an IRD or from a pirate network;

FIG. 3 is a block diagram illustrating a functional module.

SUMMARY OF THE INVENTION

The present invention is directed to addressing the effects of one ormore of the problems set forth above. The following presents asimplified summary of the invention in order to provide a basicunderstanding of some aspects of the invention. This summary is not anexhaustive overview of the invention. It is not intended to identify keycritical elements of the invention or to delineate the scope of theinvention. Its sole purpose is to present some concepts in a simplifiedform as a prelude to the more detailed description that is discussedlater.

The present invention further relates to a method for identifying atleast an identifier of a conditional access card used in a control wordredistribution system by passing information over a side channel, saidmethod comprising a modification step of the response time, of the card,to a control word request, according to a predefined function whichdepends on the identifier of the said cards.

The present invention further relates to a computer program product forremotely identifying at least one shared card over a pirate network andcomprising:

-   -   a program code for measuring the response time signature from        acquired control word from the pirate network;    -   a program code for calculating expected response time signatures        from the retrieved control words by using the set of possible        identifiers of the shared card;    -   a program code for measuring the correlation between the        measured response time signature and each one of the expected        response time signatures.    -   a program code for determining the argument of the maximum of        the correlation measurement among the set of possible identifier        of the shared card, the determined code being estimated to be        the identifier of the shared card.

While the invention is susceptible to various modification andalternative forms, specific embodiments thereof have been shown by wayof example in the drawings. It should be understood, however, that thedescription herein of specific embodiments is not intended to limit theinvention to the particular forms disclosed.

It may of course be appreciated that in the development of any suchactual embodiments, implementation-specific decisions should be made toachieve the developer's specific goal, such as compliance with systemrelated and business-related constraints. It will be appreciated thatsuch a development effort might be time consuming but may neverthelessbe a routine understanding for those or ordinary skill in the art havingthe benefit of this disclosure.

DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

With reference to FIG. 1, there is shown, in the left-hand side, alegitimate user 1 provided with

-   -   an Integrated Receiver/Decoder (IRD) 11    -   a legitimate card 12 and preferably    -   a terminal user 14 able to display a multimedia (video, audio,        data) content. A television or a computer are examples of such        terminal user 14.

The legitimate user 1 is receiving, on his IRD 11, a scrambled stream,namely a pay-tv stream, via adequate reception means such as a satellitedish, an antenna or a cable connection.

The card 12 decrypts the control word CW from the EMM and the ECM whichare forwarded thereto from the IRD 11. Subsequently, the card 12transfers back the decrypted control word CW, in plaintext form, to theIRD 11.

According to the philosophy of card sharing attack, the control word CWfurnished by the card 12 and permitting to descramble the receivedscrambled stream, is being diffused or provided on request by the cardserver 15 through the (wireless or wired) pirate network 3. It is to benoted that the card server 15 may relay more than smart card 12 output,in order to jointly serve a plurality of requests concerning the same ordifferent control words. Typically, the pirate network 3 is a two-waycommunication network, such as Internet, Intranet, a Local Area Network,a Wide Area Network or a Metropolitan Area Network.

Generally, the card 12 may be uniquely identified by a certainidentifier 13. The identifier 13 of a card is commonly an alphanumericword of a finite number of characters (generally named “serial number”or “code”). As illustrative examples, the identifier 13 of the card 12may be of the following form OA852786, 576F18C, 99E58CB001X.

In a preferred embodiment, the response time of the card 12 is used todissimulate therein its identifier 13. The response time of a card isintended here to mean the elapsed time between

-   -   the reception time, by the card 12, of an EMM/ECM in order to        provide in return the decrypted control word CW; and    -   the time at which the control word CW is decrypted, by the card        12, and it is ready to be communicated.

In fact, conventionally, the response time of a card 12 is limited tothe required time by the card 12 to make out the CW from the receivedEMM and ECM. However, the response time of a card 12 is composed of therequired time to decipher the control word CW plus an inserted timedelay which is function of the identifier 13 of the card 12.

Then, the identifier 13 of the card 12 may be coded in terms of responsetimes of the smart card 12, whereas the control word CW itself is keptunchanged. Namely, a time delay offset may be purposely included beforethe delivery of the control word CW at the level of the outgoingcommunication interface of the card 12. Explicitly, a predefined delaytime may be inserted or not before the card 12 answer to a control wordCW request in such a way that its identifier 13 may be deduced from anumerous observations of its response time (response time signature)taken by a monitoring station 2 via control word CW requesting.

The monitoring station 2, connected to the pirate network 3, is equippedwith

-   -   a processing unit 22;    -   an Integrated Receiver/Decoder (IRD) 21

Preferably, the monitoring station 2 is further provided with a terminaluser 23 able to display a descrambled stream.

The processing unit 22 is charged for:

-   -   formatting requests, towards the card server 15, for control        words CW related to the received scrambled stream on the IRD 21        (if the card server 15 works according to a pull system) or    -   selecting, among received control words CWs from the pirate        network 3, the right control word CW to decrypt the scrambled        stream received on the IRD 21 (if the card server 15 works        according to a push system);    -   load the obtained control word CW into the IRD 21 and        particularly    -   focus on the response time of cards which are the sources of the        obtained control words CWs.

The analysis of the response times of a card aims, mainly, at recreatingthe response time signature of shared cards, and consequently the cardidentifier which is encrypted within response times to control wordrequests over the pirate network 3.

It is to be noted that the monitoring station 2 may be connected fromanywhere within a communication network comprising a card sharingaccess.

With reference now to FIG. 2, the insertion decision 43 of a time delaydepends on the output of a predefined function 42. The predefinedfunction 42 is function of the card identifier 13 and the requestedcontrol word 41. It must be noted that the predefined function 42 may bethe combination or the juxtaposition of more than one function.

Preferably, the output of the predefined function 42 has one-bit lengthoutput (1=“yes”, 0=“no”), as it is shown on FIG. 2. Then, the one-bitlength output of the function 42, calculated for each control word 41request, is used to decide on the insertion or not of a predefined delaytime. For example,

-   -   if the output of the function 42 is equal to “1”, then a delay        offset is applied before the transmission of the requested        control word 41; and    -   if the output of the function 42 is equal to “0”, then no delay        to be introduced and the requested control word 41 is        communicated as soon as it is decrypted.

The function 42 is chosen in such a way that each bit of the binarywriting of the card identifier 13 is concerned by the function 42. Inother words, the definition domain of the function 42 must comprise allthe bits of the binary writing of the card identifier 13. By binarywriting of a character, the writing of the character in the alphabet {0,1} is meant.

It is to be noted that the output of the function 42 may be more than1-bit length and at any other alphanumerical form, but the insertiondecision 43 has to be adapted accordingly. Any switch-case statement maybe applied on the output of the function 42. For example, if the outputof the function 42 is equal to “01” then insert a delay, else don'tinsert a delay. Moreover, one can even define more than one time delaylevel to be inserted, such as insert the half of the time delay offsetor all the time delay offset.

FIG. 3 shows an illustrative example of the function 42. In thisexample, it is supposed that

-   -   the identifier 13 is a 32 bits word (4 bytes);    -   the control word itself is used as random source to encode the        identifier 13 of the card 12 in temporal information (response        time); and    -   the control word is 8 bytes length wherein 2 bytes are used as        checksum.

As it is shown in FIG. 3, the example of function 42 comprises a 32-to-1multiplexer, a 2-to-1 multiplexer and three functions F1, F2 and F3. A 5bit length word A is given by the function F3 from the bytes 1 and 2 ofthe currently requested control word 41. The binary word A is used toaddress the 32-to-1 multiplexer in order to select the corresponding bitfrom the card identifier 13. The selected bit B is forwarded to the2-to-1 multiplexer. Functions F1 and F2 permit, respectively, to extract1-bit length words C and D. C and D are respectively resulted from thecouple of bytes (3,5) and (6,7) of the current control word 41. Then, infunction of the value of one-bit length word B, the output E of the 2-to1 multiplexer will be the one-bit length word C or D. The output E willbe used, here, as the signature bit for the current crypto-period (orthe current control word 41). Logical functions “AND”, “OR”, “NOR”,“XOR”, “XNOR”, “NANO” or any combination of them are examples offunctions F1, F2, and F3.

In a variant embodiment, in addition to the card identifier 13, anotheror a combination of other control words are utilized by the function 42.As an example, one mentions the current control word, the alreadytransmitted control word or both.

Advantageously, the CW itself may be used as random source to encode thecard identifier in temporal information (response time of the card).

Preferably, the bits of the binary writing of the card identifier 13 arerandomly multiplexed.

In a variant embodiment, a random sequence, generated by a predefinedpseudo-random sequences generator, is used instead of the control word41.

The above tasks may be accomplished with a subroutine loaded on thesmart card. This subroutine may have the following structure:

Subroutine  delay_bit = Function(requested_control_word_ 41,card_identifier_13)   If delay_bit = 1    then wait_time x   end_if returnwhere delay_bit, Function and x are, respectively, the output of thefunction 42, the function 42, and a chosen time delay to be waitedbefore the transmission of the currently requested control word 41. Inthis example of subroutine loaded on the card 12, the insertion of thetime delay x depends on the value of delay_bit.

Preferably, the time delay to be waited x is chosen in regards

-   -   to the control word changing periodicity; and    -   to the time delay spread which may be inevitably added by the        communication channel that links the legitimate user 1 to the        monitoring station 2.

Preferably, the time delay to be waited is chosen in such a way that issignificantly inferior to the control word changing periodicity andaveragely superior (of the same order or preferably superior) to thechannel time-delay spread (maximum time delay which is introduced by thepirate network 3).

The illustrative above subroutine has to be called upon each controlword request, or, equivalently, for each crypto-period.

Once the decision on delay insertion 43 is taken and applied, therequested control word 41, through the output communication interface44, is

-   -   communicated to the IRD 11, or    -   sent to the monitoring station 2 as any other client, over the        pirate network 3.

The monitoring station 2, anywhere within a communication network havingan access to the pirate network 3, aims at recreating the card 12signature from the received control words which are decrypted by theshared card 12. At the monitoring station 2 side, the observation of thepresence/absence of such intentionally inserted time delay in comparisonwith the arrival time of an ECM at the processing unit 22 (orequivalently at the IRD 21), certainly, reveals information about theidentifier 13 of the card 12. But, obviously, the intentionally insertedtime delay will be indeed “noised” by an additive propagation delayintroduced by the communication channel over the pirate network 3(network jitter, Internet routers, satellite uplink, and modems forexample). Advantageously, the added propagation delay may beapproximated by a random process, as a noise. Thus, the randomly addednoise may be easily overcome (attenuated or even cancelled) bycollecting a large number of observations on the responses times of theshared card 12. The more noise there, the more observations are neededto better extract the useful information (the response time of sharedcard 12 and by the way the shared card identifier 13).

Aiming at recreating the response time signature of the shared card 12,the processing unit 22

-   -   calculates the difference between the arrival time of the        requested control word 41 and the arrival time, to the        processing unit 22, of its correspondent ECM; and    -   repeats the above calculation for a large observation number N        of received control words 41 from the card server 15.

More explicitly, such processing may be accomplished with a subroutineof the form:

For i=1 to N do

-   -   get ECM from the local IRD 21    -   set T_ECM=the local time    -   request, from the card server 15, the control word CW relative        to the ECM;    -   set T_CW=the local time    -   set measured_vector(i)=(T_CW−T_ECM)    -   set CW_List(i)=CW

loop i

Accordingly, the response time of the shared card 12 is measured inregards to the reception times of ECMs (or equivalently of EMMs) on thelocal IRD 21.

In order to recover the identifier 13 of the shared card 12, theprocessing unit 22 conducts a statistical analysis of the response timesignature, achieved through a correlation measure between the measuredresponse time signature (named measured_vector in the above illustrativesubroutine) and the expected one.

As the processing unit 22 does not know, a priori, the identifier 13 ofthe shared card 12, it has to calculate all the set of possible responsetime signatures of the shared card 12, given by successively using allpossible identifiers of a card of the same type as the shared card 12.Obviously, the identifier 13 of the shared card 12 exists among the setof possible identifiers. Consequently, the expected response time vectorwill be certainly the one who shows the maximum similarity (maximumcorrelation with the measured vector) with the measured one.

Accordingly, suppose that the set of possible identifiers of the sharedcard 12 counts M (M may be given by 2m, where m is the length of thebinary writing of the maximum value of identifiers). Then, for eachcandidate of this set, the processing unit 22 has to calculate theresponse time signature from the same N control words (N is the numberof observations) obtained from the card server 15. Notably, main stepsof such processing are as following

for k=1 to M % M being the number of possible identifiers in the system

-   -   For i=1 to N % N being the number of retrieved control words        delay_bit=Function(CW_list(i), one_possible_card_identifier)        expected_vector(i)=delay_bit    -   Loop i    -   Expected_matrix(:, k)=expected_vector

Loop k

It is to be noted that “Function(CW_list(i),one_possible_card_identifier)” is the same function 42 which is used bythe shared card 12, applied on the control word numbered i among the Nobserved control words and stacked in the vector named CW_list.

The output of the above illustrative subroutine may be stacked in a2-dimensional matrix (named here Expected_matrix) of size N×M andwherein

-   -   each row corresponds to one retrieved control word; and    -   each column represents a response time vector calculated with        one possible identifier of the shared card 12.

By calculating the correlation between, each column of the obtainedmatrix and the measured vector of response times, the identifier 13 ofthe shared card 12 will be, subsequently, given by the argument of themaximum value of the calculated correlation coefficients.

Such processing may be formulated as follow:

For k=1 to M % M being the number of possible identifiers in the system

-   -   Correlation_results(k)=correlation(measured_vector,        Expected_matrix(:, k))

Loop k

Estimated_Identifier_of_shared_card=arg(max(Correlation_results))

where “correlation” is a function returning the correlation coefficientbetween two vector of the same size, and “Expected_matrix(:,k)” is acolumn vector of order k from the 2-dimentional matrix“Expected_matrix”.

The loop output is a vector (named in the above example“Correlation_results”) of size 1×M which contains the correlationcoefficients and which may be plotted in function of the M possiblevalues of card identifiers.

The identifier 13 of the shared card 12 (named in the above illustrativesubroutine Estimated_Identifier_of shared_card) is given by the argumentof the maximum value of correlations coefficients plotted in function ofthe M possible identifiers of the shared card 12.

It is to be noted that when more than one shared card is linked to thecard server 15, their identifiers are the arguments of maximum values ofcorrelations coefficients plotted in function of the M possibleidentifiers. In order to easily identify the identifiers of more thanone shared card linked to the card server 15, one can proceed by

-   -   eliminating the argument of the global maximum of the        correlation coefficients plotted against the possible        identifiers;    -   repeat the above processing with the remainder of possible        identifiers until a threshold of the correlation coefficient        amplitudes.

In a variant, the correlation is done on smaller portions (sub-vectors)of the identifier that can be analyzed separately. As an example, onecan subdivide the card identifier into two sub-vectors (for example,subdividing an identifier of 32-bit length into two sub-vectors: bitsfrom 1 to 16 and bits from 17 to 32). This may be faster as it reducesthe computational complexity of the correlation calculation, to thedetriment of more additional observations (more control words to beretrieved from shared cards).

It is to be noted that different embodiments of the processing unit 22may be automatically performed by a computer program.

Once a shared card is identified, obviously, the broadcaster may takethe decision that meets his action plan (for example, deactivate thecard, exclude the card from the monthly key update, or contact theshared card owner).

Once the identifier of a shared card via a given card server isresolved, appropriate measures could follow. An example of counteractionwould be the creation of a universal ECM which deactivates every sharedcard of a specific Manufacturer. For example, an ECM could be injectedin pull systems on the pirate network 3. The card server 15 usually doesnot know if an ECM is valid/real or not since it can not decrypt it.Therefore it forwards it to the card 12 in order to be processed. Onreception of such an ECM the card 12 (after decryption) couldunderstands its purpose and, consequently, deactivates the subscriptionrights hence forcing the subscriber to call the broadcaster in order toreactivate it.

In another embodiment, a specific ECM may be dedicated for the remoteidentification of shared smart card. In fact, a pirate has no means ofunderstanding what is inside an ECM. Therefore he cannot distinguishbetween a regular ECM and a faked one. Then, a special ECM could becreated asking the shared card to respond with a CW with its identifiertherein embedded.

In another embodiment, one can extend the CW by further bits which arenot necessary for the decryption of the scrambled content but thatrepresent, in an encoded form, the card identifier. A softwareapplication, loaded on card, is in charge of embedding the cardidentifier in the control word CW in such a way an eavesdropper couldnot exclude the unwanted bits from the intercepted CW. Accordingly, ashared card will automatically reveal its identifier. Therefore, amonitoring station provided with a card sharing access can easilyidentify the shared card identifier as soon as at least one control wordis received.

In another embodiment, in a pull system, a card may be programmed to beautomatically deactivated (self-deactivation) as soon as it receives apredefined sequence of requests. Preferably, the sequence of requests isdefined in such a way is almost impossible to be unintentionallygenerated by the owner of a legitimate card. As an example of suchsequence, one can mention predefined successive requests for transitionbetween given television stations in a short time. Dedicated means maybe loaded in the card in order to detect the predefined sequence ofrequests and subsequently deactivate the card. A computer programproduct comprising

-   -   a program code for capturing the sequence over the hidden        channel;    -   a program code for correlating the captured sequence with the        predefined sequence and    -   a program code for comparing, and counteracting action        is an example of such means.

Fraudulent use counteracting of conditional access cards used for theredistribution of Control Words (shared keys) in conditional accesssystems by passing information over a side channel may be achievedthrough a predefined sequence detection function inside the said cardsand a computer program product to generate the sequence to be detected.

It is to be noted that the herein described embodiments are also validfor a local card sharing (within a home, hotel, campus or amongneighbors).

Obviously, persons skilled in the art will readily appreciate how someteaching, such. as the data staking, the subroutines implementation orthe subroutines optimization, may be modified within the spirit andscope of the appended claims.

While the invention has been described in terms of several embodiments,those skilled in the art will recognize that the invention is notlimited to the embodiments described, but can be practiced withmodification and alteration within the spirit and scope of the appendedclaims. The description is thus to be regarded as illustrative insteadof limiting and the teachings of this disclosure may be applied tosystems and methods which are similar but somewhat different than thosewhich are discussed herein.

Now that the invention has been described,

What is claimed is:
 1. A method for communicating data related to anelectronic device, the method comprising the steps of: said electronicdevice autonomously modulating the timing of a plurality of data packetssent by said electronic device, to form a timing sequence thatcorrelates to a predetermined data sequence, said timing sequencecorrelating to a signature of said electronic device.
 2. The method ofclaim 1, further comprising: said timing sequence being generated by apredefined function stored on said electronic device.
 3. The method ofclaim 1, further comprising: said timing sequence being a firstsequence; and said first sequence depending on said data and a secondsequence; said second sequence being a non-linear random sequence. 4.The method of claim 3, further comprising: said non-linear randomsequence being known to said electronic device and a monitoring stationthat receives transmissions from said electronic device.
 5. The methodof claim 1, further comprising: said modulation of said timing not beingin response to a request for a delay.
 6. The method of claim 1, furthercomprising: said electronic device autonomously modulating the phase ofthe timing of a-cyclically occurring data packets sent by saidelectronic device.
 7. The method of claim 1, further comprising: saidtiming sequence being generated locally by a non linear function usingas a first input parameter a unique identifier of said electronic deviceand as a second input parameter a datum known to the electronic deviceand a monitoring station.
 8. The method of claim 1, further comprising:transmitting said timing sequence a plurality of times; performing acorrelation analysis to compare the plurality of timing sequencetransmissions to a plurality of possible signatures of said electronicdevice to identify said unique signature.
 9. A method for communicatingdata related to an electronic device, the method comprising the stepsof: modulating the timing of a plurality of data packets sent by saidelectronic device to form a timing sequence which correlates to apredetermined data sequence, said timing sequence correlating to asignature of said electronic device.
 10. The method of claim 9, furthercomprising: said timing sequence being generated by a predefinedfunction stored on said electronic device.
 11. The method of claim 10,further comprising: said electronic device modulating the phase of thetiming of a-cyclically occurring data packets sent by said electronicdevice.
 12. The method of claim 9, further comprising: said timingsequence being a first sequence; and said first sequence depending onsaid data and a second sequence; said second sequence being a non-linearrandom sequence.
 13. The method of claim 9, further comprising: saidmodulation of said timing not being in response to a request for adelay.
 14. The method of claim 9, further comprising: said timingsequence being generated by a non linear function using as a first inputparameter a unique identifier of said electronic device and as a secondinput parameter a datum known to the electronic device and a monitoringstation.
 15. The method of claim 9, further comprising: transmittingsaid timing sequence a plurality of times; performing a correlationanalysis to compare the plurality of timing sequence transmissions to aplurality of possible signatures of said electronic device to identifysaid unique signature.
 16. An electronic device, comprising data: saidelectronic device adapted to modulate the timing of a plurality of datapackets sent by said electronic device to form a timing sequence whichcorrelates to a predetermined data sequence, said timing sequencecorrelating to a signature of said electronic device.
 17. The electronicdevice of claim 16, further comprising: said timing sequence beinggenerated by a predefined function stored on said electronic device. 18.The method of claim 17, further comprising: said electronic devicemodulating the phase of the timing of cyclically occurring data packetssent by said electronic device.
 19. The method of claim 16, furthercomprising: said modulation of said timing not being in response to arequest for a delay.
 20. The electronic device of claim 16, furthercomprising: transmitting said timing sequence a plurality of times;performing a correlation analysis to compare the plurality of timingsequence transmissions a plurality of possible signatures of saidelectronic device to identify said unique signature.
 21. The electronicdevice of claim 16, further comprising: said timing sequence being afirst sequence; and said first sequence depending on said data and asecond sequence; said second sequence being a non-linear randomsequence.
 22. A method for communicating data related to an electronicdevice, the method comprising the steps of: performing a predefinedfunction, which depends on said data, to generate a sequence of phasemodulations of communications correlated to a signature of saidelectronic device; and incorporating said sequence of phase modulationsinto communications of said data.
 23. The method of claim 22, furthercomprising: said predefined function being stored on said electronicdevice.
 24. The method of claim 22, further comprising: said predefinedfunction depending on said data and a non-linear random sequence. 25.The method of claim 24, further comprising: said non-linear randomsequence being known to said electronic device and a monitoring stationthat receives transmissions from said electronic device.
 26. The methodof claim 22, further comprising: performing a correlation analysis tocompare said sequence of phase modulations of communications to aplurality of possible sequence of phase modulations of communications toidentify said data.
 27. The method of claim 22, further comprising: saidmodulation of said phase not being in response to a request for a delay.28. A method for communicating data related to an electronic device, themethod comprising the steps of: performing a predefined function, whichdepends on said data, to generate a sequence of timing modulations ofcommunications correlated to a signature of said electronic device; andincorporating said sequence of timing modulations into communications ofsaid data.
 29. The method of claim 28, wherein: said timing modulationsof said communications comprises delaying transmission of individualcommunications.
 30. An electronic device, comprising data: saidelectronic device adapted to perform a predefined function, whichdepends on said data, to generate a sequence of phase modulations ofcommunications correlated to a signature of said electronic device; andsaid electronic device adapted to incorporate said sequence of phasemodulations into communications of said data.
 31. The method of claim30, further comprising: said predefined function depending on said dataand a non-linear random sequence.
 32. The method of claim 31, furthercomprising: said non-linear random sequence being known to saidelectronic device and a monitoring station that receives transmissionsfrom said electronic device.
 33. An electronic device, comprising data:said electronic device adapted to perform a predefined function, whichdepends on said data, to generate a sequence of timing modulations ofcommunications correlated to a signature of said electronic device; andsaid electronic device adapted to incorporate said sequence of timingmodulations into communications of said data.
 34. The method of claim33, further comprising: said predefined function depending on said dataand a non-linear random sequence.
 35. The method of claim 34, furthercomprising: said non-linear random sequence being known to saidelectronic device and a monitoring station that receives transmissionsfrom said electronic device.